get function declaration in C mode with tags

Hi,
How to get declaration in C mode with tags in Emacs. I only know how to get definition of self defined functions. But how to jump to their declarations and also how to get the declarations of C++ standard library functions and classes? Thanks!

Hi,
How to get declaration in C mode with tags in Emacs. I only know how to get definition of self defined functions. But how to jump to their declarations and also how to get the declarations of C++ standard library functions and classes? Thanks!